run_diff.sh shellcheck fixes

* Replace backticks with $()
* Double-quote filenames that might conceivably contain troublesome special chars (*, space etc)

Author: smowton

scripts/run_diff.sh

@@ -2,8 +2,8 @@
 
 set -e
 
-script_folder=`dirname $0`
-absolute_repository_root=`git rev-parse --show-toplevel`
+script_folder=$(dirname "$0")
+absolute_repository_root=$(git rev-parse --show-toplevel)
 mode=$1
 modes="CPPLINT | DOXYGEN"
 
@@ -16,7 +16,7 @@ then
   exit 1
 fi
 
-if ! [[ -e $script_folder/filter_by_lines.py ]]
+if ! [[ -e ${script_folder}/filter_by_lines.py ]]
 then
   echo "Filter script could not be found in the $script_folder directory"
   echo "Ensure filter_by_lines.py is inside the $script_folder directory then run again"
@@ -31,13 +31,13 @@ then
     exit 1
   fi
 
-  if ! [[ -e $script_folder/cpplint.py ]]
+  if ! [[ -e "${script_folder}/cpplint.py" ]]
   then
     echo "Lint script could not be found in the $script_folder directory"
     echo "Ensure cpplint.py is inside the $script_folder directory then run again"
     exit 1
   else
-    cmd='$script_folder/cpplint.py $file 2>&1 >/dev/null'
+    cmd='${script_folder}/cpplint.py $file 2>&1 >/dev/null'
   fi
 elif [[ "$mode" == "DOXYGEN" ]]
 then
@@ -78,26 +78,26 @@ else
     git_merge_base_end="HEAD"
 fi
 
-git_start=`git merge-base $git_start $git_merge_base_end`
+git_start=$(git merge-base $git_start $git_merge_base_end)
 
 cleanup()
 {
-  rm -f $diff_file $added_lines_file
+  rm -f "$diff_file" "$added_lines_file"
 }
 
 trap cleanup EXIT
 
-diff_file=`mktemp`
-added_lines_file=`mktemp`
+diff_file=$(mktemp)
+added_lines_file=$(mktemp)
 
 # Pass the output through iconv to remove any invalid UTF-8 (diff_to_added_lines.py will die otherwise)
 
-git diff $git_start $git_end | iconv -t utf-8 -c > $diff_file
+git diff $git_start $git_end | iconv -t utf-8 -c > "$diff_file"
 
 # Get the list of files that have changed, that end with lintable extensions
-diff_files=`git diff --name-only $git_start $git_end | grep "\.\(\(cpp\)\|\(hh\)\|\(cc\)\|h\)$" || true`
+diff_files=$(git diff --name-only $git_start $git_end | grep "\.\(\(cpp\)\|\(hh\)\|\(cc\)\|h\)$" || true)
 
-$script_folder/diff_to_added_lines.py $diff_file $absolute_repository_root > $added_lines_file
+"${script_folder}/diff_to_added_lines.py" "$diff_file" "$absolute_repository_root" > "$added_lines_file"
 
 for file in $diff_files; do
   file=$absolute_repository_root/$file
@@ -109,7 +109,7 @@ for file in $diff_files; do
 
   # Run the linting script and filter:
   # The errors from the linter go to STDERR so must be redirected to STDOUT
-  result=`eval $cmd | $script_folder/filter_by_diff.py $file $added_lines_file $absolute_repository_root`
+  result=$(eval $cmd | "${script_folder}/filter_by_lines.py" "$file" "$added_lines_file" "$absolute_repository_root")
 
   # Providing some errors were relevant we print them out
   if [ "$result" ]